Light emitting device and backlight module

Abstract

A light emitting device includes a laser light source, a converging lens, and a diverging lens. The laser light source is configured to emit combined red, green, and blue laser beams. The combined red, green, and blue laser beams appear to be collimated white light beams. The converging lens is configured to receive the collimated white light beams. The diverging lens faces the converging lens and is configured to diverge the collimated white light beams exiting from the converging lens. A distance between the diverging lens and the converging lens is larger than the focal length of the converging lens.

What is claimed is: 
     
       1. A light emitting device comprising:
 a laser light source configured to emit red, green, and blue laser beams, the red, green, and blue laser beams combining to form a collimated white light beam; 
 a converging lens configured to receive the collimated white light beam; 
 a diverging lens facing the converging lens and configured to diverge the collimated white light beam exiting from the converging lens, and a distance between the diverging lens and the converging lens being larger than the focal length of the converging lens; and 
 a diffusion plate, the diffusion plate and the converging lens positioned at opposite sides of the diverging lens, and the diffusion plate facing the diverging lens. 
 
     
     
       2. The light emitting device of  claim 1 , wherein the laser light source comprises a first laser unit for emitting green laser beams, a second laser unit for emitting red laser beams, and a third laser unit for emitting blue laser beams, a first dichroic mirror, and a second dichroic mirror, the blue laser beams being parallel with the red laser beams and perpendicular to the green laser beams, the first dichroic mirror and the second dichroic mirror are arranged on a light path of the first laser unit, the first dichroic mirror corresponds to the second laser unit, the second dichroic mirror corresponds to the third laser unit, green laser beams from the first laser unit passes through the first dichroic mirror and the second dichroic mirror, red laser beams from the second laser unit are reflected toward the second dichroic mirror by the first dichroic mirror and pass through the second dichroic mirror, and blue laser beams from the third laser unit are reflected by the second dichroic mirror. 
     
     
       3. The light emitting device of  claim 1 , wherein the diverging lens comprises a light incident surface, a light output surface, and a peripheral surface, the light incident surface and the light output surface are positioned at opposite sides of the diverging lens, the peripheral surface is interconnected between the light incident surface and the light output surface, the light incident surface defines a cavity, the light output surface is outwardly curved, and the peripheral surface has a frosted region. 
     
     
       4. The light emitting device of  claim 3 , wherein the diverging lens is symmetric relative to an optical axis thereof, the cavity is symmetric relative to the optical axis and has a semi-elliptic section, the cavity comprises a circular opening, and a depth of the cavity is larger than the radius of the opening. 
     
     
       5. The light emitting device of  claim 1 , further comprising a reflecting mirror for receiving and reflecting the collimated white light beams. 
     
     
       6. A backlight module comprising:
 a light emitting device comprising:
 a laser light source configured to emit red, green, and blue laser beams, the red, green, and blue laser beams combining to form a collimated white light beam; 
 
 a converging lens configured to receive the collimated white light beam; and 
 a diverging lens facing the converging lens and configured to diverge the collimated white light beam exiting from the converging lens, and a distance between the diverging lens and the converging lens being larger than the focal length of the converging lens; and 
 a diffusion plate, the diffusion plate and the converging lens positioned at opposite sides of the diverging lens, and the diffusion plate facing the diverging lens. 
 
     
     
       7. The backlight module of  claim 6 , wherein the laser light source comprises a first laser unit for emitting green laser beams, a second laser unit for emitting red laser beams, and a third laser unit for emitting blue laser beams, a first dichroic mirror, and a second dichroic mirror, the blue laser beams being parallel with the red laser beams and perpendicular to the green laser beams, the first dichroic mirror and the second dichroic mirror are arranged on a light path of the first laser unit, the first dichroic mirror corresponds to the second laser unit, the second dichroic mirror corresponds to the third laser unit, green laser beams from the first laser unit passes through the first dichroic mirror and the second dichroic mirror, red laser beams from the second laser unit are reflected toward the second dichroic mirror by the first dichroic mirror and pass through the second dichroic mirror, and blue laser beams from the third laser unit are reflected by the second dichroic mirror. 
     
     
       8. The backlight module of  claim 6 , wherein the diverging lens comprises a light incident surface, a light output surface, and a peripheral surface, the light incident surface and the light output surface are positioned at opposite sides of the diverging lens, the peripheral surface is interconnected between the light incident surface and the light output surface, the light incident surface defines a cavity, the light output surface is outwardly curved, and the peripheral surface has a frosted region. 
     
     
       9. The light emitting device of  claim 8 , wherein the diverging lens is symmetric relative to an optical axis thereof, the cavity is symmetric relative to the optical axis and has a semi-elliptic section, the cavity comprises a circular opening, and a depth of the cavity is larger than the radius of the opening. 
     
     
       10. The light emitting device of  claim 6 , further comprising a reflecting mirror for receiving and reflecting the collimated white light beams. 
     
     
       11. A backlight module comprising:
 a number of light emitting devices each comprising:
 a laser light source configured to emit red, green, and blue laser beams, the red, green, and blue laser beams combining to form a collimated white light beam; 
 
 a converging lens configured to receive the collimated white light beam; and 
 a diverging lens facing the converging lens and configured to diverge the collimated white light beam exiting from the converging lens, and a distance between the diverging lens and the converging lens being larger than the focal length of the converging lens; and 
 a diffusion plate, the diffusion plate and each of the converging lenses positioned at opposite sides of each of the diverging lenses, and the diffusion plate facing each of the diverging lenses. 
 
     
     
       12. The backlight module of  claim 11 , wherein each of the laser light sources comprises a first laser unit for emitting green laser beams, a second laser unit for emitting red laser beams, and a third laser unit for emitting blue laser beams, a first dichroic mirror, and a second dichroic mirror, the blue laser beams being parallel with the red laser beams and perpendicular to the green laser beams, the first dichroic mirror and the second dichroic mirror are arranged on a light path of the first laser unit, the first dichroic mirror corresponds to the second laser unit, the second dichroic mirror corresponds to the third laser unit, green laser beams from the first laser unit passes through the first dichroic mirror and the second dichroic mirror, red laser beams from the second laser unit are reflected toward the second dichroic mirror by the first dichroic mirror and pass through the second dichroic mirror, and blue laser beams from the third laser unit are reflected by the second dichroic mirror. 
     
     
       13. The backlight module of  claim 11 , wherein each of the diverging lenses comprises a light incident surface, a light output surface, and a peripheral surface, the light incident surface and the light output surface are positioned at opposite sides of the diverging lens, the peripheral surface is interconnected between the light incident surface and the light output surface, the light incident surface defines a cavity, the light output surface is outwardly curved, and the peripheral surface has a frosted region. 
     
     
       14. The backlight module of  claim 13 , wherein each of the diverging lenses is symmetric relative to an optical axis thereof, the cavity is symmetric relative to the optical axis and has a semi-elliptic section, the cavity comprises a circular opening, and a depth of the cavity is larger than the radius of the opening. 
     
     
       15. The backlight module of  claim 6 , wherein each of the light emitting devices further comprises a reflecting mirror for receiving and reflecting the collimated white light beams.